Messages in this thread | | | From | David Laight <> | Subject | RE: [PATCH] x86/mce: Fix set_mce_nospec() to avoid #GP fault | Date | Mon, 10 Sep 2018 13:52:24 +0000 |
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From: Linus Torvalds > ... > You could literally do something like > > /* Make it canonical in case we flipped the high bit */ > addr = (long)(addr<<1)>>1;
Isn't it safer to use a mask and let the compiler decide if two shifts are a good implementation?
addr &= ~HIGH_MAGIC_BIT;
ISTR fixing a bug in gld where it had (foo << 16) >> 16 instead of foo & 0xffff. Didn't work well on 64bit.
(I may need to recompile that old gcc/gld again. Failed miserably last time I tried.)
David
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